RE: Maximum Db_cache_size?

Thank you for the idea, Steve.
In my system the advice view shows increasing values only from the current 4GB to 8GB. What I am after are *algorithmical* Oracle problems(well, issues) like all kind of hash buckets chains waits, etc. I do not think cache advisor is taking into account those issues. At least v$db_cache_advise has no timing column in 9i.  

-----Original Message-----
From: Steve Perry [mailto:sperry_at_sprynet.com] Sent: 19. júní 2006 11:11
To: Laimutis Nedzinskas
Subject: Re: Maximum Db_cache_size?

can't you use v$db _cache_advice to tell you the optimal setting for database cache? I think it exists in 9i. there are lots of queries on the web to show the point of diminishing returns.

On Jun 19, 2006, at 05:54 AM, Laimutis Nedzinskas wrote:

> Just follow up:
>
> May be it is somewhat easier to think about the problem in terms of
> "db buffer cache scalability".
> Generally the scalability is not linear at the best.
> Often the scalability graph has a turning point when adding more
> resources only makes performance worse.
> The question is what RAM value(or formula) is the turning point for
> Oracle buffer cache, if any?
>
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-
> bounce_at_freelists.org] On Behalf Of Laimutis Nedzinskas
> Sent: 19. júní 2006 10:44
> To: oracle-l_at_freelists.org
> Subject: Maximum Db_cache_size?
>
> Is it good or bad to use all available (not used for other purposes,
> eg.
> shared pool or pga) RAM for buffer cache?
> I am talking about 32GB RAM range.
>
> Oracle is not in-memory database but anyway - memory access is faster
> than disk access.
> However I understand that the way(algorithms) Oracle uses RAM may have
> a practical turning point when adding more RAM will only slow down
> things.
>
> Therefor the question is:
>
> - is Oracle(9.2 version) better at utilizing RAM(say, 10-20GB) for
> buffer cache?
>
> - or is it it is better to let file system to utilize this RAM for
> file cache?
>
> - none of the above, stay with moderate RAM usage (few gigabytes for
> buffer cache) just because buffer cache hit ration is good (98-99%)? I
> would just like to point out that 1% of disk ("raw") access makes up a
> considerable response time, may be 50% or so.
>
> Thank you in advance,
> Laimis N.
>
> Fyrirvari/Disclaimer
> http://www.landsbanki.is/disclaimer
> --
> http://www.freelists.org/webpage/oracle-l
>
>
> Fyrirvari/Disclaimer
> http://www.landsbanki.is/disclaimer
> --
> http://www.freelists.org/webpage/oracle-l
>
>

Fyrirvari/Disclaimer
http://www.landsbanki.is/disclaimer

--
http://www.freelists.org/webpage/oracle-l